Series type multiple thermal jet propulsion system



May 24, 1960 H. 1. JOHNSON SERIES TYPE MULTIPLE THERMAL JET PROPULSICN SYSTEM Filed Sept. 13, 1955 2 Sheets-Sheetl 1 May 24, 1960 H. J. JOHNSON 2,937,494

SERIES TYPE MULTIPLE THERMAL JET PROPULSION SYSTEM Filed Sept. 13, 1955 2 Sheets-Sheet 2 INVENTOR. Horace da' mes JZr/Sa l BY #frown/LVS.

MIjlnited States Patent() SERIES TYPE MULTIPLE THERMAL JET PROPULSION SYSTEM Horace James Johnson, 519 Washington Road,

- Grosse Pointe, Mich.

Filed sept. 1s, 195s, ser. No. 533,933 rz claims.. (c1. en -35.6)

This invention relates to jet propulsion power plants and, more particularly, to a series type multiple thermal jet propulsion system.- This application is a continuationin-part of the applicants copending application, Serial No. 50,271, tiled September 21, 1948, now Patent Number 2,721,444, issued October 25,1955, for Series Type Multiple Ram Jet Propulsion System.

Thermal jet propulsion power plants may be divided into the turbo jet, pulse jet, ram jet and rocket types. The turbo jet presently enjoys wider use than the other types because in the turbo jet plant some form of rotary compressor is utilized to initially pressurize the air entering the combustion chamber, to thereby materially increase the velocity of the products of combustion at rela-v tively low air speeds. The pulse jet and the rocket types are relatively short-lived in the present state of development. In the ram jet, which is a continuous tiring unit operating with a continuous iiow of air to produce a continuouspropulsion thrust, air is rammed from the ambient atmosphere into the combustion chamber by the velocity of-the lunit and without the benefit of mechanical compressionand also without the use of 'valves or other moving parts. Such units are also known as athodyds. As used herein, throughout the specification and claims, the term ram jet is intended to refer to a power plant of the athodyd type. With the turbo jet, pulse jet and rocket types of propulsion, sufficient velocity can be developed at the outlet nozzle to effect take-off of air-craft, for example, while in the ram jet, insufficient jet velocity has thus far been developed for this purpose.

Turbojet power plants present much greater cooling problems than the other types and it has been necessary to constantly force extra air through them, resulting in considerable unbur'ned oxygen at the exhaust'. Heretofore, additional thrust has been obtained by providing an'after-burner of the ram jet type at the outlet of a turbo jet plant, `such after-burner receiving the entire exhaust of the turbo jet with no separate source of air being provided, so that combustion in the after-burner is supported entirely by excess oxygen from the exhaust of the turbo jet.

The present invention contemplates the provision of a novel jet propulsion power plant utilizing two or more thermal jet units wherein the outlet of the iirst unit communicates with the inlet of the second unit and'wherein cooling means is provided in heat exchange relationship with respectto the outlet ofthe first unit so as to'increase the density and the mass of the hot gases in the first unit without decreasing the velocity thereof, thereby enabling the charging rate and the pressure inthe second unit to be increased and increasing the eillciency of both units. The size of the second or subsequent units or stages is not limited by the size and characteristics of the rst or earlier stages.

An object of the present invention is to overcome disadvantages in prior iet propulsion plants of the indicated character and to provide an improved thermal Yjet prof pulsion power plant system which facilitates a higher ratio of jet velocity to air speed, at relatively low air speeds, than has heretofore beenobtainable with power" plants of this character.

Another object of the invention is to provide an improved thermal jet type power plant comprising two or .more thermal jet units arranged in tandem, with the jet issuing from the nozzle of-the first unit into the combustion chamber of the succeeding unit to increase the etticiency of both units.V r

=Another object of the invention is to provide a novel thermal jet type propulsion power plant of the character described in whichv `air drawn into the trailing unit or units g is caused to enter the latter at an accelerated rate.

Another object of the invention is to provide au irnproved series type 'multiplel thermal jet propulsion system that is economical to manufacture andv assembly, durable,

efficient and reliable in operation.

The above as well as other objects and advantages of Y the present invention will become apparent from the following description, the appended claims and the acoompanying drawing wherein:

Figure 1 is a side elevational view,`with portions in l section, of a jet propulsion plant embodying the present invention;

Fig 2 is an enlarged view of a portion of the power I shown as comprising two longitudinally aligned ram jet propulsion units, generally designated 10 and v11. Theunit 10 .includes a diffuser section 12 having an inlet vopening which, when mounted on an aircraft, faces f The unit 10 y in the direction of motion of the aircraft. also includes a combustion chamber 14, a constricted throat portion 15 and a divergent portion 16 which might,

if the unit 10 were used alone, be opened to discharge directly to the atmosphere. injector to accelerate-the gases entering the second unit 11, however, and in order to increase the density of the hot gases in the rst unit Without decreasing the velocity thereof, a cooling section, generally designated j 17, is provided which'includes a substantially straight section 17A for reversing the diverging tendency of the gases and a section 17B which converges suicieutly to oiset the decrease in volume and maintain the velocity of the gases. In this embodiment of the invention, the cooling section is cooled by a jacket structure trough which fuel is passed, and the cooling section discharges into the trailing unit 11.

The unit 11 is substantially larger than the unit 10 in the embodiment of the invention illustrated,`and is preferably formed as a single unit having an inlet opening 18'k at its forward end-which leads into a convergent wall 19A spacedly surrounding the rear cooling and discharge portions of the front unit 10, around which air from the inlet 18 is thus admitted. vThe outlet of the cooling section of the forward unit 10 terminates in forwardly spaced relationship with respect toa constricted throat portion -19B provided lin the trailing unit 11, and the hot gases ow through the throat portion 19B to a divergent, pressure increasing diffuser section 20 and from there past burners 36 to a combustion chamber 21 and a discharge nozzle opening 22.

The thickened wall of the unit 11 intermediate the opening 18 land the throat poriton 19B is provided with aA reduced peripheral portion having an external thread'ZS `PatentedkMay 24, 1960,

The unit 10 is used as an for receiving the' internally threaded end of a hollow smooth cylindrical casing or shell 24 thereon, theouter pe-4 riphery of the shell being ilush with the outer periphery of the supporting thickened wall of the unit 11 so that a streamlined and unbroken surface is provided thereby. The rear end of the shell iits tightly upon the thickened rear wall of the unit -11 and the last-mentioned thickened wall provides a continuation of the unbroken streamlined surface. The shell 24 also bridges the reduced intermediate portions of the rear unit 11 to provide an annular fuel feeding and inlet cooling chamber 37 through which the fuel is delivered to the burners 36.

The cooling section 17 of the unit 10 is defined by double walls 27 and 27A between which are disposed two spaced helical ribs 25 and 26 of like pitch, the ribs 25 and 26 extending for substantially the entire length of the cooling section A17 and co-acting with the frusto-conical walls 27 and 27A to thereby define alternate spiral passages 28 and 29 between the Walls 27 and 27A. The passages 28 and 29 are thus in intimate heat conductive relationship with the sections 17A and 17B. A

The rst ram jet unit is supported within the rear ram jet unit .11 with the outlet of the cooling section 17 of the front unit terminating forwardly of the throat portion 19B of the second unit. A plurality of radially arranged, spaced streamlined struts 30 are provided which include reduced bosses 31 at the outer ends which secure the struts within the wall of the unit 11 forwardly of the throat portion 19, the struts also being tightly con necetd, as by welding, to the outer wall 27 at their inner ends. The spaces between the struts 30vpermit communication of the throat portion 19B of the unit 11 with the atmosphere through the opening l18. 'I'he unit 10 is also supported by the unit 11 at a point rearwardly of the throat by a plurality of radially arranged, spaced, streamlined struts 32 which have reduced diameter externally threaded bosses 33 at their inner ends received within a series of threaded apertures formed in the wall of the unit 10, the outer ends of the struts 32 being xcd to the periphery of the wall of the unit 11. The spaces between the struts 32 also permit the passage of air from the ambient atmosphere to the interior of the unit 11 by way ofthe spaces between the struts 30.

A series of radially arranged fuel burners 34 are mounted within the combustion chamber 14 of the unit 10 and connected by conduits 35 with a suitable fuel supply (not shown) externally of the system. In a similar manner, the combustion chamber 21 of the unit 11 has mounted therein a series of radially arranged fuel burners 36 (only one being shown in Fig. 1) but instead of being supplied directly from the fuel source, the burners 36 are supplied from the chamber 37 located between the outer periphery of the wall of the unit 1,1 and the inner periphery of the shell 24, the burners 36 communicating with the chamber 37 through conduits or pipes 38. Fuel is supplied to the chamber 37 by suitable conduits (not shown) which may be connected to a series of radially spaced tapped ports 39 formed in the wall of the unit 11 adjacent the opening 18. The ports 39 register with passageways `40 formed in the struts 32, the passageways 40 discharging into the helical spiral passageways 28 and 29 previously referred to. One passageway 40 communicates with the helical passageway 28 and the other communicates with the helical passageway 29. Theoutlet of the passageway 29 communicates with the chamber 37 by way of a passageway 42 formed in one of the struts 30 and the outlet of passageway 28 communicates with chamber a its velocity drops and its pressure increases in the diffuser section 12. At the burners 34 the high pressure air is mixed with the fuel supplied by conduits 35 and burned in the combustion chamber 14. The gases resulting therefrom are expanded and accelerated to pass at considerable velocity through the throat portion 15 and then through the cooling section 17 to emerge therefrom as a jet having a high velocity. Instead of utilizing the thrust of the jet issuing from the section 17 solely as a means for deriving propulsion, the ram jet type of propulsion plant is improved by the present invention in accordance with which the jet issuing from the section 17 passes into the second unit `11. The high speed gases leaving the front unit create a low pressure area forwardly of the throat portion 19B of the second unit, thus inducing the air from the surrounding atmosphere entering the opening 18 to accelerate in its passage to the throat 19B where it continues to accelerate as it mixes with the high speed gases emanating from the front unit until the mixture reaches the diffuser section 20 of the'rear unit in which the burned gases and the air are nearly at the same velocity. As the latter mixture approaches the combustion chamber 21 its velocity decreases and its pressure increases, the pressure reaching a maximum value at the burners 36 where the fuel from the conduits 38 is injected into the mixture and burned by the burners 36. The resulting burned gases are expanded and accelerated through the nozzle 22 attaining a maximum velocity as they issue as a jet from the nozzle.

It will be apparent that by the novel arrangement hereof the jet of the first unit is utilized not merely for thrust purposes as in conventional power plants but for increasing the entrance velocity of the atmospheric air to the second combustion chamber which, of course, not only increases the velocity of the jet issuing from the nozzle 22 of the second unit but also aids in total combustion within the second combustion chamber.

It will be understood that other stages may be 'used in addition to the two stages shown whereby the use of one stage to increase the velocity of the next stage will increase the maximum pressure of the latter stage and thereby increase the overall efficiency of the plant.

While the increased entrance velocity will increase the entrance temperature, a net gain will be obtained nevertheless because as more stages are utilized the higher will be the maximum pressure in the last stage.

The length of the throat portion 19B must be great enough so that the air and the burned gases will be moving at substantially the same velocity when they reach the diffuser section 20. The cross sectional area of the throat 19B is only varied throughout its length suiciently to compensate for variations of volume of the mixture due to temperature change and variations of the velocity of the burned gases and air as they approach a common velocity. The air will increase in volume at about the same rate that the burned gases decrease in volume during the transfer of heat in mixing so that the total volume will remain approximately the same. Similarly the int crease in velocity of the air is offset by a decrease in 37 by way of a passageway 43 in another of the struts velocity of the burned gases so that the cross sectional area between the two sections will be approximately constant.

Another embodiment of the invention is illustrated in Fig. 3 and is comprised of a rocket propulsion unit, generally designated 100, and a ram jet propulsion unit, generally designated 102, the units and 102 being substantially coaxially aligned and being shown in installed relationship with respect to a schematically illustrated Wing section 104. The rocket unit 100 includes a combustion chamber 106, a constricted throat portion 108 and a divergent portion 110 which might, if the unit 100 is used alone, be opened to discharge directly to the atmosphere. The unit 100 is used as an injector to accelerate the gases entering the ram jet unit 102 and, in order to increase the density of the hot gases emanating from the rocket unit withoutl decreasing the Avelocity thereof, a cooling section 112 is provided which includes a substantially straight section 114 for reversing thediverging tendency of the `gases, and a section 116 which converges sufficiently to oifset the decrease in volume and maintain the velocity of the gases. In this embodiment of the invention, the cooling section is cooled by a jacket structure through which coolant tiows, the coolant being recycled. It will be understood, however, that, if desired, fuel could be utilized as the coolant, the fuel being discharged to a suitable reservoir for the ram jet unit.

The ram jet unit 102 is substantially larger than the rocket unit 100, and includes an inlet opening 118 at its forward end which leads into a convergent section 120. The outlet of the rocket unit terminates in forwardly spaced relationship with respect tothe convergent section 1'20 and the convergent section 120 merges with a throat section 122, the hot gases flowing through the throat section 122 through a divergent pressure increasing diffuser section 124 and from there past burners 126 to a combustion chamber 128 which c orresponds to the combustion chamber 21 in the embodiment of the invention illustrated in Figs. `1 and 2. The products of combustion then flow outwardly through a discharge v nozzle in the maner previously described.

The rocket unit 100 includes spaced walls 130 and 132 between which spaced helical ribs 134 and 136 are disposed, the ribs extending for substantially the entire length of the rocket unit and co-acting with the walls 130 and 132 to define spiral passageways 138 and 140. The passageway 138 is separated from the passageway 140 by an intermediate wall 142 which extends annularly around the rocket unit 100 intermediate the walls 130 and 132.

The cooling portion of the rocket unit 100 is supported Within the forwardvportion of the ram jet unit 102 so that the outlet of the cooling lsection 112 of the rocket unit terminates forwardly of the throat portion 122 of the ram jet unit. A plurality of radiall extending angularly spaced streamlined struts 144 are provided which are fixed to the rocket and ram jet units in any desired or conventional manner so as to support the cooling section 112, while the forward portion of the rocket is supported on a mounting section 146 carried by the wing structure 104. The spaces between the struts 144 permit communication of the throat portion 122 of the ram jet unit with the ambient atmosphere through the inlet opening 118.

Fuel lis supplied to the combustion chamber 106 through a conduit 148 while van oxidizer is supplied to the combustion chamber through a conduit 150. The series of radially arranged fuel burners 126 mounted in the combustion chamber are supplied with fuel through conduits 152 which communicate with a suitable fuel supply (not shown) externally of the system.

Coolant lis supplied to the sectionv 138 of the cooling system through a conduit 154 and s returned from the section 138 through an outlet conduit 156 while the chamber 140 of the cooling section is supplied with coolant through a conduit 158, the coolant flowing outwardly from the section 140 through an outlet conduit 160. l Y

The coolant owing through the sections 138 and 140 defined by the helically extending ribs 134 and 136 serves to cool and dissipate some of the heat from the combustion gases emerging from the combustion chamber of the rocket. With such a construction, the cooling means increase the density and the mass of the hot gases emergin'gt from the rocket without decreasing the velocity of the gases, thereby enabling the charging lrate and the pressure on the ram jet to be increased, and materiallyv increasingvthe eiiciency of both units.

Assuming that the propulsion plantis mounted on an aircraft, the rocket unit Y100 operates as a conventional @naar toeliet." FuelA andv an oxidizer are supplied tlirouglr the-.jV

conduits 148 and 150respectively, and the products of combustion are accelerated and pass at considerable velocity through 4the throat portion 108 and then through the cooling section 112 so as to emerge from the outletv nozzle as a jet having a high velocity. Instead of utiliz ingthe thrust of the rocket issuing from the cooling section 112 solely as a means of deriving propulsion the eiciency of the power plant is improved by the present invention in accordance with which the jet issuing from the cooling section 112 Vpasses into the `ram jet unit 102. The high speed gases leaving the rocket unit create a low pressure area forwardly of the throat portion 122 of the ram jet unit, thus inducing the air from the ambientY atmosphere entering the opening 118 to accelerate in its passage to the throat 'portion 122 where it continues to accelerate as it mixes with the high speed gases emanating from the rocket until the mixture reaches the diffuser section 124 of the ram jet unit in which the burned gases and the air are substantially the same velocity. As the latter mixture approaches the combustion chamber 128,'- its velocity decreases and its pressure increases, the pressure reaching a maximum value at the burners 126 where fuel from the conduits 152 is injected into the kmixture and burned. The resultant burned gases are expanded and accelerated through theoutlet nozzle of the ram jet unit attaining a maximum velocity as they issue as a jet from the outlet nozzle of the ram jet unit.

It will be apparent that by the novel arrangement of this embodiment of the invention, the jet of the rocket unit is utilized not merely for lthrust populsion but is also utilized for increasing. the entrance velocity of the atmospheric air to the combustion chamber of Ithe ram jet unit which, of course not only increases the velocity of the jet issuing from the outlet nozzle of the ram jet unit but also aids in total combustion within the combustion chamber of the ram jet unit.

The length of the throat portion 122 of the ram jet unit is preferably great enough so that the -air and the products of combustion of the rocket will be moving at substantially the same velocity when they reach the combustion chamber 128. The cross sectional area of the throat portion 122 is only varied throughout its length sufliciently to compensate for variations of volume of the mixture due to temperature changes and variations of V.the velocity of the products of combustion and entering air as they approach a common velocity. The entering air will increase in volume at approximately the same -rate that the burned gases decrease in Volume during the transfer of heat in mixing so that the total volume Another embodiment of the invention is illustrated in Fig. 4 and is comprised of a Vturbo jet propulsion unit, generally designated 200, and an after-burner, generally designated 202, the turbo jet 200 and the after-burner 202 beingV substantially coaxially aligned. The turbo jet unitk 200 includes an exhaust section 204 which defines an annular outlet nozzle 206, -an exhaust cone 208 being disposed in the central portion of the outlet nozzle in the'conventional manner. In order to reduce the temperature of the gases issuing from lthe exhaust nozzle 206 into the after-burner 202, a cooling section 210 is provided whichr includes a converging section 212, a throat section 214 'and a diverging section 216, the sections 206 yand 212 converging sufficiently to offset the decrease in volumel and maintain the velocity of the gases. The cooling sec tion 210 maybe cooled by a jacket structure through which the fuel is passedand lsuch cooling section dis charges into the inlet of the after-burner 202.

The after-burner 202 includes a diverging section 218,V

a combustion chamber 220 and an outlet nozzle portion l222. The diverging section 218 serves as a prcssurein ,1, ,s creasing diffuser section and the gases ow from the diffuser section through the combustion chamber 220 and discharge from the outlet nozzle 222.

The walls 224 and 226V of `the unit 200 and the cone 208, respectively, define spiral passageways 228 and 230, the passageway 228 also extending through the cooling section 210 while the passageway 230 terminates adjacent the apex of the cone 208 The cone 208 is supported within the exhaust nozzle 206 of the turbo jet unit 200 by a plurality of radially extending struts 232 and 234, the opposite ends of which are fixed to the walls 224 and 226. The spaces between the struts 232 and 234 permit the passage of the hot gases through the exhaust nozzle 206 of the turbo jet unit. The struts 232 and 234 define fluid passageways through which coolant flows from the spiral passageway 228 into the spiral passageway 230 and from the spiral passageway 230 into an outlet conduit 236 which communicates with the passageway 230. The coolant is supplied to the spiral passageway 228 through an inlet conduit 233, the conduit 238 being connected to a suitable source of supply (not shown).

A plurality of burners 240 are mounted in the combustion chamber 220, the burners 240 being supplied with fuel through suitable conduits 242 which communicate with the fuel reservoir. Y

Assuming that the propulsion plant is mounted on an aircraft, for example, the unit 200 operates as a conventional turbo jet. After the hot gases pass through the turbine blades 244, the gases flow through the outlet nozzle 206 and the cooling section 210. The gases fowing through the outlet nozzle 206 contain substantial amounts of unburned oxygen, and the gases issuing from the discharge nozzle 206 flow through the cooling section 210 directly into the after-burner 202. As the gases flow through the diffuser section 218, the velocity decreases and the pressure increases, the pressure reaching a maximum value at the burners 240 where fuel is sprayed into the gases and burned. The resulting products of combustion are expanded and accelerate through the nozzle 222, attaining a maximum velocity as they issue as a jet from the nozzle 222.

The cooling means which is in heat exchange relationship with respect to the outlet of the turbo jet unit increases the density of the hot gases discharged from the turbo jet unit without decreasing the velocity thereof, thereby materially increasing the efficiency of both the turbo jet unit as a pump and the after burner as a jet unit. Since the cooling between the turbo jet unit and the ram jet unit increases the mass of the gases without decreasing the velocity thereof, the charging rate and the pressure in the after-burner are materially increased with the result that the pressure ratio and the efficiency of the after-burner is increased.

Another embodiment of the invention is illustrated in Fig. 5, this embodiment of the invention including a turbo jet unit 300 and a ram jet unit 302, the turbo jet 300 and the ram jet 302 being substantially coaxially aligned. The turbo jet unit 300 includes a diffuser section 304, a compressor section 306, a combustion section 308, a turbine section 310 and an outlet nozzle 312. The turbo jet 300 functions as an injector to accelerate the gases entering the ram jet unit 302, and in order to reduce the temperature of the gases delivered from the turbo jet unit into the ram jet unit, a cooling section 314 is incorporated in the exhaust section of the tur-bo jet. In accordance with the present invention, the outlet nozzle 312 of the turbo jet unit converges sufficiently to ofset the decrease in volume of the hot gases passing therethrough and maintain the velocity of such gases. The cooling section includes a jacket structure through which fuel is passed and the gases are discharged from the cooling section into the inlet of the ram jet unit 302.

The ramjet unit 302 includes an inlet opening 316 which leads into a convergent section 318 spacedly surrounding the rear cooling and dischargeA portions of the turbo jet unit 300'around which air from the inlet 316 is admitted. The air from the inlet 316 and gases from the turbo jet unit are lead through a throat section 320 to either a converging or divering pressure increasing diffuser section, combustion chamber and discharge nozzle in the manner previously described. The wall 322 ofthe discharge section of the turbo jet and the wall 324 of the discharge cone 326 of the turbo jet define longitudinally extendinghelical passageways 328 and 330, respectively, through which fuel or other suitable coolant flows to cool the gases owing through the discharge nozzle 312. The turbo jet unit 300 is supported within the ram jet unit with the outlet of the turbo jet unit lterminating forwardly of the throat 320 of the ram jet unit, the rear section-of the' turbo jet unit being supported by a plurality of angularly spaced radially extending streamlined struts, such as 332 and 334. The struts 332 define uid conduits 336 through which the coolant flows into the passageways 328 and 330. The coolant flows through thepassageways 328 and 330, and the coolant leaves the passageway 330 through a conduit 338 and flows into the passageway 328. The coolant then flows from passageway 328 through an outlet conduit 340 defined by the strut 334. The conduits 336 and 340 may be connected to a suitable reservoir or may be included in the fuel supply line through which the fuel is supplied to the ram jet unit 302.

Assuming that the propulsion plant is mounted on an aircraft, for example, the unit 300 will operate as a conventional turbo jet unit. Air is rammed into the diffuser section 304 and ows through the compressor section 306 into the combustion chamber 308 where fuel is mixed with the high pressure air and burned. The products of combustion then flow through the turbine section 310 where sufficient energy is extracted from the hot gases to drive the compressor section' 306. The gases then flow through the exhaust nozzle 312 and emerge therefrom as a jet having a relatively high velocity. The cooling means which is in heat exchange relationship with respect to the outlet of the turbo jet unit increases the density of the hot gases without decreasing the velocity thereof. Since the cooling means also increases the mass of the gases without decreasing the velocity thereof, the charging rate and pressure in the ram jet unit are increased. The gases emerging from the turbo jet unit create a low pressure area forwardly of the throat portion 320 of the ram jet unit,thus inducing the air from the ambient atmosphere entering the inlet opening 316 to accelerate'in its passage to the throat portion 320 where it continues to accelerate as it mixes with the high speed gases emanating from the turbo jet unit. When the mixture reaches the diffusersection of the ram jet unit the burned gases and the air are nearly at the t same velocity andas. the mixture approaches the combustion chamber of the ram jet unit the velocity decreases and the pressure increases in the manner previously described so that the pressure reaches a maximum value at the burners of the ram jet unit. Fuel is then added in the combustion chamber of the ram jet unit in the manner previously described, and the resulting burned gases are expanded and accelerated through the outlet nozzle of the ram jet unit so as to attain a maximum velocity as they issue as a jet from the ram jet unit.

While preferred embodiments of the invention have been shown and described, it will be understood that various changes and modifications may be made without departing from the spirit of the invention.

What is claimed is:

1. A series type multiple thermal jet propulsion system comprising, in combination, a forward thermal jet propulsion unit, a trailing thermal jet propulsion unit, said forward unit including a body having a combustion chamber section and a converging outlet nozzle section to the 'rear of and communicating with said combustion chamber section, said forward unit body also including. an expansion section interposed between said combus-v tion chamber section and said outlet nozzle section and effective to accelerate the gases emanating from said combustion chamber section, said trailing unit .including a body having an inlet section, a combustion chamber section to the rear of and communicating with said inlet section, and an outlet nozzle section communicating with saidcombustion chamber section of said trailing unit, said outlet nozzle section of said forward unit communicating with the inlet section of the trailing unit, and cooling means in heat exchange relationship with respect to the outlet nozzle section of said forward unit, said cooling means being effective to` increase the mass velocity product per square inch of the gases flowing through said outlet nozzle section of said forward unit after the gases have passed through said expansion section of said forward unit, said outlet nozzle section of said forward unit having aA cross-sectional area progressively decreasing as afunction of the cooling capacity of said cooling means whereby the velocity of the gases iiowing through said outlet nozzle section of the forward unit is maintained substantially constant while the volume of the gases decreases and the density of the gases increases.

2. A series type multiple thermal jet propulsion systern comprising, in combination, a forward thermal jet propulsion unit, a trailing thermal jet propulsion unit, each of said units including a body having an inlet section, a combustion chamber section to the rear of and communicating with said inlet section, and an outlet section communicating with said combustion chamber section, said outlet section of the forward unit being in the form of a converging nozzle and communicating with the inlet section of the trailing unit, said forward unit body also including an expansion section interposed between said combustion chamber section and said outlet section of the forward unit and effective to accelerate the gases emanating from said combustion chamber section of the forward unit, and cooling means in heat exchange relationship with respect to the outlet section of the forward'unit, said cooling means being effective to increase the mass velocity product per square inch of the gases flowing through said outlet section of the forward unit after the gases have passedthrough said expansion section of the forward unit, said outlet section of the forward unit having a cross-sectional area progressively decreasing as a function of the cooling capacity of said cooling means whereby the velocity of the, gases owing through said outlet section of the forward unit is maintained substantially constant while the volume of the gases decreases and the density of the gases increases.

3. In aseries type multiple thermal jet propulsion system, the combination including a forward thermal jet propulsion.` unit, a trailing thermal jet propulsion unit, each of said units including a body having an inlet section, a combustion chamber section to the rear of and communicating with said inlet section, and an outlet section communicating with said combustion chamber section, said outlet section of the forward unit being in the form of'aV converging nozzle` and communicating with the inlet section of the trailing unit, said forward unit body also including an expansion section interposed between saidcornbustion chamber section and 'said outlet section'of the forward unit and effective to accelerate the gases emanating from said combustion chamber section of the forward unit, said body of said trailing unit also including forwardly opening portions communicating the inlet section thereof directly with the atmosphere, and cooling Y means in heat exchange relationship with respect to the outlet section of the forward unit, said cooling means being effective to increase the mass velocity product per square inch of the gases owing through said outlet section of the forward unit after the gases have passed through said expansion section of the forward unit, said aber;

outletI section of the forward unit having a cross-sectionalf. area progressively decreasing as a function of the coolingI capacity ofsaid cooling means whereb-y the Velocity of the gases flowing through said outlet section of the.for-. ward unit is maintained substantially constant while the volume of the gases decreases and the density of the gases increases. 4. A series type multiple thermal jet propulsion sys tem comprising, in combination, a pair of thermal jet propulsion units disposed in substantially tandem relationship, each of said units including a body having an inlet section, a combustion chamber section to the rear of and communicating with said inlet section, and an outlet section communicating with said combustion chamber section, said outlet section of the forward unit being in the form of a converging nozzle and communicating with the inlet section of the trailing unit, said'fo'rward unit body also including an expansion section interposed between said combustion chamber section andv said outlet section of the forward unit and effective to accelerate the f gases emanating from said combustion chamber section of the forward unit, and cooling means in heat exchangey relationship with respect to the outlet section of the forward unit, said cooling means being effective to increase the mass VVelocity product per square inch of the gases flowing through said outlet section of the forward unit after the gases have passed through said expansion sectionV of the forward unit, said outlet vsection of the forward unit having a cross-sectional area progressively decreasing as a function of the cooling capacity of said cooling means whereby the velocity of the gases owing throughA said outlet section for the forward unit is maintained'substantially constant while the volume of the gases decreases and the density of the gases increases.

5. A system as defined in claim 4 wherein the second unitl is a ram jetunit, the inlet section of said second unit communicating with the atmosphere as well as with said outlet section of the first unit.

6. A series type multiple thermal jet propulsion system comprising, in combination, a turbo jet unit, a ram jet disposed in tandem relationship with respect to said Y turbo jet unit, each of said units including a body having v an inlet section, a combustion chamber section to the rear of and communicating with said inlet section, and an out- A jetunit, said cooling means being elfective to increase the' mass velocity product per square inch of the gases owmg through said outlet section of the turbo jet unit after the gases have passed through said expansion section ofthe turbo jet unit, said outlet section of the turbo jet unit hav.-H

ing a cross-sectional area progressively decreasing'asv a function of the cooling capacity of said cooling means, whereby the velocity of the gases owing through saidA outletV section of the` turbo jet unit is maintained substantially constant while the volume of the gases decreases and the density of the gases increases.

7. A series type multiple thermal jet propulsion systern comprising, in combination, a forward thermal jet propulsion unit, a trailing thermal jet propulsion unit, said forward unit being in the form of a rocket and including a body having a combustion chamber section and a converging outlet nozzle section to the rear of and communicating with said combustion chamber section, said forward unit body also including an expansion section interposed between said combustion chamber sec- 11- t o n and said outlet nozzle section and effective to accelerate the gases emanating from said combustion chamber section, said trailing unit being in the -form of a ram jet and including a body having an inlet section, a combustion chamber section to the rear of and communicating with said inlet section, and an outlet nozzle section communicating with said combustion chamber section, said outlet nozzle section of said forward unit communicating with the inlet section of the trailing unit, and cooling means in heat exchange relationship with respect to the outlet nozzle section of said forward unit, said cooling means being effective to increase the mass velocity product per square inch of the gases flowing through said outletnozzle section of said forward unit after the gasesjhave passed through said expansion section of said forward unit, said outlet nozzle section of said forward unit having a cross-sectional area progressively decreasing as a function of the cooling capacity of said cooling means whereby the velocity of the gases flowing through said outlet nozzle section of the forward unit is maintained substantially constant while the volume of the gases decreases and the density of the gases increases.

8. A series type multiple thermal jet propulsion system comprising, in combination, a forward thermal jet propulsion unit, a trailing thermal jet propulsion unit, said units being disposed in substantially coaxial tandem relationship, each of said units including a body having an inlet section, a combustion chamber section to the rear of and communicating with said inlet section, and an outlet section communicating with said combustion chamber section, said outlet section of the forward unit being in the form of a converging nozzle and communicating with the inlet section of the trailing unit, said forward unit body also including an expansion section interposed between said combustion chamber section and said outlet section of the forward unit and effective to accelerate the gases emanating from said combustion chamber section of the forward unit, and cooling means in heat exchange relationship with respect to the outlet section of the forward unit, said cooling means being effective to increase the mass velocity product per square inch of the gases flowing through said outlet section of the forward unit after the gases have passed through said expansion section of the forward unit, said outlet section of the forward unit having a cross-sectioanl area progerssively decreasing as a function ofthe cooling capacity of said cooling means whereby the velocity of the gases flowing through said outlet section of the forward unit is maintained substantially constant while the volume of the gases decreases and the density of the gases increases.

9. A system as defined in claim 8 wherein the forward unit is a turbo jet.

10. A system as defined in claim 8 wherein the forward unit is a turbo jet and the trailing unit is a ram jet, the inlet section of said ram jet communicatingwith the atmosphere as well as with the outlet section ofthe turbo jet.

11. A series type multiple thermal jet propulsion system comprising, in combination, a forward ram jet propulsion unit, a trailing ram jet propulsion unit, each of said units including a body having an inlet section, a combustion chamber section to the rear of and communicat-l ing with said inlet section, and an outlet section communicating with said combustion chamber section, said outlet section of the forwardunit being in the form of aconverg'ing nozzle and communicating with the inlet section of the trailing unit, said forward unit body also in-V cluding an expansion section interposed between said combustion'chamber section and said outlet section of the forwardunit and effective to accelerate the gases emanan ing from said combustion chamber section of the forward unit, said trailing ram jet unit also including means connecting the inlet section thereof directly with the atmosphere, and cooling means in heat exchange relationship with respect to the outlet section of the forward unit, said cooling means being effective to increase the mass velocity product per square inch of the gases flowing through said outlet section of the forward unit after the gases have passed through said expansion section of the forward unit, said outlet section of the forward unit having a crosssectional area progressively decreasing as a function of the cooling capacity of said cooling means whereby the velocity of the gases flowing through said outlet section of the forward unit is maintained substantially constant` while the volume of the gases decreases and the density of the gases increases. Y

12. A series type multiple thermal jet propulsion system comprising, in combination, a forward thermal jet propulsion unit, a trailing thermal jet propulsion unit, said forward unit including a body having a combustion chamber section and a converging outlet nozzle section to the rear of and communicating with said combustion chamber section, said forward unit body also including an expansion section interposed between said combustion chamber section and said outlet nozzle section and effective to accelerate the gases emanating from said combustion chamber section, said trailing unit including a body having an inlet section, a combustion chamber section to the rear of and communicating with said inlet sec-` tion, and an an outlet nozzle section communicating with said combustion chamber section, said outlet nozzle section of said forward unit communicating with the inlet section of the trailing unit, cooling means in heat exchange relationship with respect to the outlet nozzlesecf tion of said forward unit, and cooling means in heat exchange relationship with respect to the inlet section of the trailing unit, said cooling means being effective to increase the mass velocity product per square inch of the gases flowing through said outlet nozzle section'of said forward unit after the gases have passed through said expansion section of said forward unit, said outlet nozzle section of said forward unit having a cross-sectional area progressively decreasing as a functionof the cooling capacity of said cooling means whereby the velocity of the gases flowing through said outlet nozzle'section of the forward unit is maintained' substantially constant while the volume of the gases decreases and the density of the gases increases.

References Cited in the file of this patent UNITED STATES PATENTS 1,375,601 Morize Apr. 19, 1921,

2,670,597V Villemejane Mar. 2, 1954 2,721,444-v Johnson Oct. 25, 1955 2,735,263 Charshaian Feb. 2l, 1956 FOREIGN PATENTS 522,163 France Mar. 22, 1921 

